[YeGoblynQueenne]

It's not just about terrain and the original version is seeded with a prototype image that the algorithm learns a pattern from that it then replicates with variations.

It's not described that way but it is a one-shot pattern learning algorithm that is much more interesting than just a procedural generation algorithm, or even a constraint solver as others have said.

See the link to the creator of the original version given by platz in the sister comment. There's more going on than just "procedural terrain generation".